Electronic – Designing with fuses…when to use


Most circuits that I have designed in the past deal with low voltages…sensors, communicating with other chips, etc. When would I need to consider the addition of fuses into my designs? Sometimes I need to control higher voltage devices like motors that require 24V for example.
Fuses protect against shorts and large spikes in current. When should these be introduced?

Best Answer

Fuses protect against fires. If you have a non-current limited supply (like a connection to mains power or a large battery) and you develop a short on your PCB, it's possible to ignite something.

A fuse won't:

  • Operate at its rated current indefinitely.
  • Blow at currents above its rating instantly.
  • Protect against very fast current spikes.
  • Protect against overvoltage conditions if the current isn't abnormal.
  • Protect semiconductors or ICs against damage - The fuse is slower than the silicon.
  • Protect a person against damage - You can still be electrocuted by a fused circuit.
  • Protect anything if it's on the wrong side of the short.

But it will usually prevent large currents from flowing through it long enough to start a fire.